while all of that is quite possible to do (and indeed has been done a few times and posted here), it's a bit of complexity involved.
Detecting temperature requires a thermistor (thermal-sensitive resistor), and detecting light will require a photosensor (used for those auto-sensing night lights). Left and right turn signals are a simple matter of looking for voltage on a particular line.
The problem comes when it comes to converting those voltages (or resistance values) generated by your sources to something the computer can use, and knowing what to do with them from that point. Check out a couple threads that I started regarding this stuff. I learned here that one of the best ways to convert those values (on the computer side) is through the game/MIDI port found with some sound cards.
You're going to have to do some circuit building, however, for the conversion of the raw voltages/resistance generated by your sensors. This is a grey area for me, but it has been covered here. You might have to search until your mouse is ready to break, but it IS here. Google is also very helpful. I'll post some links here if I can find anything...